Mechanism of small molecule inhibition of Plasmodium falciparum myosin A informs antimalarial drug design.

Malaria results in more than 500,000 deaths per year and the causative Plasmodium parasites continue to develop resistance to all known agents, including different antimalarial combinations. The class XIV myosin motor PfMyoA is part of a core macromolecular complex called the glideosome, essential for Plasmodium parasite mobility and therefore an attractive drug target. Here, we characterize the interaction of a small molecule (KNX-002) with PfMyoA. KNX-002 inhibits PfMyoA ATPase activity in vitro and blocks asexual blood stage growth of merozoites, one of three motile Plasmodium life-cycle stages. Combining biochemical assays and X-ray crystallography, we demonstrate that KNX-002 inhibits PfMyoA using a previously undescribed binding mode, sequestering it in a post-rigor state detached from actin. KNX-002 binding prevents efficient ATP hydrolysis and priming of the lever arm, thus inhibiting motor activity. This small-molecule inhibitor of PfMyoA paves the way for the development of alternative antimalarial treatments.

Spatiotemporal higher-order chromatin landscape of human histone gene clusters at histone locus bodies during the cell cycle in breast cancer progression.

Human Histone Locus Bodies (HLBs) are nuclear subdomains comprised of clustered histone genes that are coordinately regulated throughout the cell cycle. We addressed temporal-spatial higher-order genome organization for time-dependent chromatin remodeling at HLBs that supports control of cell proliferation. Proximity distances of specific genomic contacts within histone gene clusters exhibit subtle changes during the G1 phase in MCF10 breast cancer progression model cell lines. This approach directly demonstrates that the two principal histone gene regulatory proteins, HINFP (H4 gene regulator) and NPAT, localize at chromatin loop anchor-points, denoted by CTCF binding, supporting the stringent requirement for histone biosynthesis to package newly replicated DNA as chromatin. We identified a novel enhancer region located âˆ¼ 2 MB distal to histone gene sub-clusters on chromosome 6 that consistently makes genomic contacts with HLB chromatin and is bound by NPAT. During G1 progression the first DNA loops form between one of three histone gene sub-clusters bound by HINFP and the distal enhancer region. Our findings are consistent with a model that the HINFP/NPAT complex controls the formation and dynamic remodeling of higher-order genomic organization of histone gene clusters at HLBs in early to late G1 phase to support transcription of histone mRNAs in S phase.